The present invention relates to containers formed of sheet material, and more particularly to containers that are instantly manually erectable by an end user from a stackable container precursor.
A regular slotted container (xe2x80x9cRSCxe2x80x9d) is a conventional and widely used type of rectangular shipping container which is formed-up from a knocked-down-flat (xe2x80x9cKDFxe2x80x9d) container precursor having four wall panels, four top flap panels and four bottom flap panels. The KDF container precursor is formed by securing together edges of a blank including the aforementioned panels to form an endless loop. In the KDF state, a RSC precursor has a substantially uniform, two-layer thickness, with the top and bottom flaps extending outward from, and coplanar with, their associated wall panels. The uniform two-layer thickness permits the RSC precursors to be stacked in an even, space efficient manner, for bulk shipping and/or storage of the same.
A RSC is typically formed by an end user pressing on opposing edges (the folding scores) of the KDF precursor. The opposed forces cause the precursor to open into a rectangular tubular shape, by way of rotations of the wall panels about their hinged connections to each other. Next, each of the four bottom flaps is manually pivoted inwardly to a position generally orthogonal with respect to the tubular rectangular structure. Typically, a pair of opposing minor bottom flaps are first pivoted inwardly, then the remaining pair of opposing major bottom flaps are manually pivoted inwardly over the minor flaps and are affixed to each other with tape or the like. Once the desired contents are loaded into the container, the four top flap panels are pivoted inwardly in a similar fashion, to form a top closure of the container.
Due to their simple construction, RSCs are economical to manufacture and, in general, serve well their intended purpose. In their collapsed state, RSCs can be easily and stably stacked for bulk shipping and storage. At their point of use, RSCs may readily be set-up, loaded and sealed by an end user. As mentioned, however, set-up of the boxes requires multiple steps. In particular, formation of a RSC requires that a user manually pivot inwardly each of the bottom flaps into a bottom-forming position. While holding the bottom flaps in position, the user must affix the flaps with adhesive tape or the like. Thus, set-up of a RSC requires time and effort on the part of the end user to manually position and affix the bottom flaps.
In comparison to RSCs, automatic bottom containers are known which are designed to simplify the box set-up procedure. Exemplary of known automatic bottom containers is Thompson U.S. Pat. No. 3,057,535. The container of Thompson is erected by separating opposing side walls to thereby cause bottom flaps, which are adhesively bonded together and sandwiched between opposing side walls, to automatically pivot outwardly to an interlocking, bottom forming position.
The Thompson container blank has four side wall panels and four bottom flaps connected thereto. Two of the bottom flaps have a flap extension with adhesive on an interior surface. A container precursor is made by folding the bottom flaps inward to double-back on an inside surface of a respective side wall, folding the flap extensions to double-back again, and then folding over the side walls to connect lateral edges of the blank to thereby form an endless loop of adjoined panels. The flap extensions bond to exterior surfaces of the adjacent bottom flaps as the side walls are folded over onto each other and connected. Each of the bottom flaps, and doubled-back flap extensions, are sandwiched between the side walls, thereby creating up to five-layers of thickness in the regions of the flap extensions.
As compared to RSCs, automatic bottom containers, such as disclosed by Thompson, require additional manufacturing steps for forming the relatively complicated arrangement of bottom flaps. In general, this leads to a lower overall rate of production. For example, multiple passes of a blank through a forming machine may be required to apply glue, and provide folds, in all the necessary places.
A further drawback of known automatic bottom containers is that the container precursors do not lie uniformly flat. The collapsed, automatic bottom container precursors vary in thickness from, e.g., five-layers to two-layers. When stacking precursors of such irregular thickness, bulges form, e.g., at the five-layer thickness regions, and slope off in surrounding directions toward the areas having lesser numbers of layers. When such precursors are stacked, the bulges may cause the precursors to sit unstably, and the stack to unstably tilt. Varying the placement of the varying thicknesses within a stack, by rotating or otherwise shifting the precursors relative to each other, may tend to stabilize the stack, but such special positioning adds to the costs of packaging the precursors for distribution to end users.
A further drawback of known automatic bottom containers is that, once set-up, the bottom surface of the container is not uniformly planar and uninterrupted. For example, with reference to the Thompson design, the flap extensions are bonded to exterior container surfaces, thereby creating protruding edges on the exterior bottom surface of the container, which may tend to catch or snag on supporting surfaces.
Accordingly, a sheet material container that would form-up more rapidly and with less manual effort than a RSC, and which could be manufactured more economically than known automatic bottom containers, would be highly desirable.
In view of the foregoing, it is a principal object of the present invention to provide a sheet material container (and precursor/blank therefor) with a configuration of end flap panels that causes the panels to automatically pivot into a container closure (e.g., bottom) forming position upon erecting the container precursor from a KDF condition.
It is a more specific object of the present invention to provide a container as aforesaid, which may be manufactured largely in the manner of a RSC, with minor modifications to existing machinery used to manufacture RSCs.
It is a related object of the present invention to provide a container precursor as aforesaid, that has a substantially uniform two-layer thickness in a KDF condition, thereby permitting even and stable stacking of the precursors for bulk shipping and storage.
The foregoing and other objects are achieved, in whole or in part, by the various aspects of the present invention. In a first aspect, the present invention is embodied in a sheet material container precursor. Therein, a plurality of wall panels of sheet material are hingedly connected to each other along respective fold lines to form a closed loop of wall panels that may be collapsed to a two layer knocked-down-flat condition and erected to form a rectangular tubular shape. A plurality of end flap panels of sheet material are hingedly attached to, and depend from, ends of respective ones of the plurality of wall panels. A pair of adjacent ones of the end flap panels, which lie in face-to-face relation in the two layer knocked-down-flat condition, and which extend orthogonally to each other in the rectangular tubular shape, have inside surfaces attached to each other to thereby form a corner attachment. One of the pair of end flap panels comprises a diagonal fold line adjacent the corner attachment. When the closed loop of wall panels is erected from the two layer knocked-down-flat condition to form the rectangular tubular shape, the corner attachment causes: (1) the one end flap panel to pivot inwardly about its hinged attachment to a respective wall panel; (2) a first corner region of the one end flap panel to fold back upon an outside surface of the one end flap panel, about the diagonal fold line; and (3) the other of the pair of end flap panels to pivot inwardly about its hinged attachment to a respective wall panel. Thereby, the pair of end flap panels are moved toward respective end closure forming positions in which the pair of end flap panels partially overlap with each other and extend inwardly with respect to the wall panels.
In a second aspect, the invention is embodied in a container formed-up from a sheet material container precursor as aforesaid. The plurality of wall panels of sheet material are erected to form the rectangular tubular shape. The plurality of end flap panels extend inwardly with respect to the rectangular tubular shape, to form a closed end of the rectangular tubular shape. The corner region of the one end flap panel is folded back upon an outside surface of the one end flap panel to form three overlaid panel portions at a position corresponding to the corner attachment.
In a third aspect, the invention is embodied in a blank of sheet material for forming a collapsible container. The blank includes a plurality of wall panels of sheet material which are hingedly connected to each other along respective fold lines. End ones of the plurality of wall panels are connectible to each other to form a closed loop of wall panels that may be collapsed to a two-layer knocked-down-flat condition, and erected to form a rectangular tubular shape. A plurality of end flap panels of sheet material are hingedly attached to, and depend from, ends of respective ones of the plurality of wall panels. A pair of adjacent ones of the plurality of end flap panels are foldable onto each other about one of the respective fold lines hingedly connecting a corresponding pair of the plurality of wall panels, such that respective corner forming side and end edges of said pair of end flap panels extend along one another. One of the pair of end flap panels comprises a diagonal fold line which extends from the side edge of the one end flap panel to the end edge of the one end flap panel. The diagonal fold line defines a first corner region which, when the pair of end flap panels are folded onto each other, substantially overlies a corresponding region of the other of the pair of end flap panels. A second corner region of the one end flap panel, opposite the first corner region, is cut-away from a third one of the plurality of end flap panels such that, when the pair of end flap panels are folded onto each other, a portion of the other of the pair of end flap panels, extending between the one end flap panel and the third end flap panel, remains uncovered by the one end flap panel.
These and other aspects and features of the invention will be readily apparent and fully understood from the following detailed description of the preferred embodiments, taken in connection with the accompanying drawings.